1. Field of the Invention
The present invention relates to an optical system of a projector, and more particularly, to an optical system of a portable projector and a mobile communication terminal using the same.
2. Discussion of the Related Art
The recent tendency of display devices is to provide a large screen size as well as lightness and thinness. Of such display devices, projectors have been greatly highlighted because they can realize a large screen of 100 inches or more.
Such a projector is a display device which projects an image generated from a micro device such as a liquid crystal display (LCD) panel, a reflective liquid crystal on silicon (LCOS) panel, or a digital micro-mirror device (DMD) panel, onto a screen, thereby displaying the image.
Generally, such a projector is classified into a single panel type, a double panel type, or a triple panel type in accordance with the number of micro devices used in the projector.
In a single panel type projector, white light is separated into color light components in a time-division manner, and the separated color light components are illuminated to a single micro device. In a double panel type projector, white light is separated into color light components in a space-division and time-division manner, and the color light components are illuminated to two micro devices. In a triple panel type projector, white light is separated into color light components in a space-division manner, and the color light components are illuminated to three micro devices.
FIG. 1 is a schematic view illustrating an arrangement of a general single panel type projector. FIG. 2 is a perspective view illustrating an arrangement of a general triple panel type projector.
As shown in FIG. 1, the single panel type projector includes a light source 2, a color drum 3, a rod lens 4, illumination lenses 5 and 6, a micro device 7, a prism 8, and a projection lens unit 1.
In the illustrated single panel type projector, light emitted from the light source 2 is separated into red, green, and blue light beams while passing through the color drum 3. The separated light beams are modulated to have uniform brightness while passing through the rod lens 4. The light beams are then incident on the micro device 7 after passing through the illumination lenses 5 and 6 and the prism 8.
The incident light beams have an image signal while passing through the micro device 7, and are projected on a screen after passing through the prism 8 and projection lens unit 1.
Also, as shown in FIG. 2, the triple panel type projector includes dichroic mirrors 9 to separate light emitted from the light source 2 into red, green, and blue light beams. The separated red, green, and blue light beams are incident on corresponding LCD panels 10, respectively. The incident light beams are then composed to be projected onto a screen via the projection lens unit 1.
The conventional projectors having the above-mentioned arrangement, however, have a problem in that they require not only a great number of optical elements, but also an excessively large installation space due to a three dimensional arrangement of an optical system thereof.
Such an arrangement of the optical system makes it impossible to reduce the entire size of the projector.
Also, the conventional projectors generally suffer from the loss of light because a traveling path of the light from the light source to the projection lens unit is long. Therefore, the conventional projectors have a limitation to display a bright and vivid image.
Due to the three dimensional arrangement of the optical system, furthermore, the conventional projectors have a problem in that an arrangement of optical elements is unstable.